EP0427951B1 - Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren - Google Patents

Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren Download PDF

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Publication number
EP0427951B1
EP0427951B1 EP90119037A EP90119037A EP0427951B1 EP 0427951 B1 EP0427951 B1 EP 0427951B1 EP 90119037 A EP90119037 A EP 90119037A EP 90119037 A EP90119037 A EP 90119037A EP 0427951 B1 EP0427951 B1 EP 0427951B1
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European Patent Office
Prior art keywords
distortions
fading
frequency
spectrum
measurement
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90119037A
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English (en)
French (fr)
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EP0427951A3 (en
EP0427951A2 (de
Inventor
Adelio Conti
Paolo Troyer
Rocco Nobili
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Alcatel Lucent Italia SpA
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Alcatel Italia SpA
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Publication date
Priority claimed from IT02216089A external-priority patent/IT1237649B/it
Priority claimed from IT02215989A external-priority patent/IT1237648B/it
Priority claimed from IT02223189A external-priority patent/IT1237669B/it
Application filed by Alcatel Italia SpA filed Critical Alcatel Italia SpA
Publication of EP0427951A2 publication Critical patent/EP0427951A2/de
Publication of EP0427951A3 publication Critical patent/EP0427951A3/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/005—Control of transmission; Equalising
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/318—Received signal strength
    • H04B17/327—Received signal code power [RSCP]

Definitions

  • the present invention concerns a system for detecting data spectrum distortion in transmission, e.g. distortions caused by selective fading; the present invention refers in particular to a system for detecting possible in-band dispersions, wherein dispersion means an amplitude dispersion.
  • the number 'n' of filters that are used is typically limited to two or three.
  • an amplitude equalizer which sums up the output of two circuit means having opposite characteristics. That is, use is made of a positive slope first order amplitude equalizer, and a negative slope first order amplitude equalizer is provided in parallel thereto. Further, a feedback means is added to enable automatic amplitude equalization.
  • the aim of the invention is to provide a particularly simple and efficient system that can be easily embodied and allows to eliminate the inconvenience of the methods using several filters and in particular permits to obtain information over the "whole band", i.e. a measurement of the dispersion over the whole band, that is less sensitive to the interference frequencies.
  • the system according to the invention defined in claim 1 which is substantially based on identifying a dispersion over the whole band, or an amplitude distortion over the whole band (that is less sensitive to interference frequencies).
  • the received signal is submitted to two distortions applied in parallel, having substantially equal slopes and opposite signs; each applied distortion is suitable to establish a variation of the average power spectrum in transient condition, these two average powers are measured and the signals resulting from these measurements are compared.
  • the equivalence or difference of the signals indicates the absence or presence of fading, respectively.
  • the results of the measurement of the two average powers are different in the presence of fading, even if the notch frequency (fo) is out of band.
  • the voltages related to the power level according to a certain characteristic curve are compared.
  • the difference between the voltages is taken as a quality index for the in-band distortion: the higher the voltage difference, the higher the distortion and vice versa.
  • a switching criterion or control signal is retrieved from the IF signature providing the information for the distortion measurement.
  • a leading frequency may be derived that extends over a frequency range much wider than the conventional 10 ⁇ 6 range.
  • the circuit for the embodiment of the distortion measurement according to the invention includes two parallel distortion blocks with equal slopes, but opposite signs, two average power testers and a comparator.
  • Figure 1 shows a circuit of the device according to the invention and Figures 2 to 11, 13 and 14 illustrate different configurations of the circuit.
  • FIGS 12 and 15 to 17 represent advantageous applications.
  • the circuit of Figure 1 includes: A) a transmission means symbolically represented by block H ( ⁇ ) (10), B) two blocks in parallel B1(1) and B2(2), C) two detectors of average power R1 and R2 and D) a comparator A0(3) of the signals obtained from said detectors R1 and R2. Signal Eu at the output from A0(3) indicates the measure of the dissymmetry due to selective fading.
  • Signal e'(t) is the transmitted signal and forms the input of the common block, representing the transmission channel H( ⁇ ) (10), and the output of this block e(t) is the input signal of the system that measures dissymmetry.
  • H( ⁇ ) In the absence of fading, H( ⁇ ) remains constant upon a frequency variation, hence, there will be no amplitude distortion.
  • the transfer function formed by H( ⁇ ) and block B1 the two cascaded blocks of Figure 2 will be obtained. Inside the blocks, the trend of the module versus frequency is represented. If the transfer function formed by H( ⁇ ) and block 2 is considered, the two cascaded blocks of Figure 3 will be obtained.
  • the module H( ⁇ ) has an in-band trend that can be represented by a slope assumed to be the slope of H( ⁇ ) in Figure 5 and Figure 6.
  • the output of the detectors is a voltage that is related, according to a certain characteristic curve, to the power level at the input; the higher the power level, the higher the voltage value at the output and vice versa; in this manner, it is clear that, if the average power of data spectrum 1 (SD1) is higher than the average power of data spectrum 2 (SD2), the output voltage of detector R1 is higher than the output voltage of detector R2.
  • SD1 average power of data spectrum 1
  • SD2 average power of data spectrum 2
  • the difference of the two voltages not only indicates whether fading is present or not, but also whether fo is located on the right-hand or on the left-hand side of f C ; further this difference is also a quality index of the value of band distortion, i.e. the higher the difference between the two voltages, the greater the distortion is, and vice versa.
  • the system according to the invention has further advantages, developments and applications.
  • the dispersion is considered as amplitude distortion.
  • the block diagram shown in Figure 12 represents once again the dissymmetry tester, at the output of which are supplied two voltages V1 and V2 related to the dissymmetry of the data spectrum.
  • the information related to fading with a central notch is achieved by summing the two detected voltages and comparing the sum with a reference voltage representing absence of fading.
  • An Automatic Gain Control is presumably provided at the input of the distortion detector.
  • the AGC is absolutely necessary in this embodiment because the module is inserted after a locking device. This causes a level stability upon a fading parameters change, which makes processing in the central band of the data spectrum inefficient .
  • an AGC with a selective filter Fs is added.
  • the AGC becomes redundant.
  • the dispersion tester has three voltages V1, V2, V3; these voltages supply the information related to the amplitude distortion caused by selective fading.
  • the distortion measurement thus obtained allows to generate a switching criterion or control, to oppose selective fadings that can create dispersions, i.e. amplitude distortions on the data spectrum modulated on a transmission carrier wave.
  • the method used is the parity method, i.e. the number of even ones or odd ones, counted in each receive frame, are compared during a certain time period with the number of even ones or odd ones, counted in the same transmit frames.
  • the measurement block for the error rate supplies an alarm.
  • the invention is also useful for the generation of the switching criterion which should not have any of the above mentioned inconveniences and supply well spaced and enlarged signatures.
  • the invention allows for advantageous applications in the system structure.
  • the device is supposed to be used in a (1+1) switching system having a transmission channel and a standby channel, switching to the standby radio beam is considerably leading or in anticipation with respect to the error conditions.
  • the device makes switching more efficient and prevents that it is carried out in error conditions.
  • SES Severely Errored Seconds
  • DM Degraded Minutes
  • RBER Residual Bit Error Ratio
  • an IF measurement of the distortions in the data spectrum is performed, and the information of this measurement is processed for drawing a curve (IF signature) with reference to a BER signature equal to the conventional rate 10 ⁇ 6; this IF signature represents the curve of the values corresponding to the distortions due to selective fading, which evolve towards an error condition for the adopted modulation-demodulation type.
  • the IF signature generates a frequency leading or in anticipation by extending over a frequency range much more extended than the range of the 10 ⁇ 6 signature, with respect to the amplitudes of which it shows wider amplitudes with a considerable gap between the two curves.
  • the device of the present invention is characterized in that a circuit consisting of at least two triggers is added to the distortion measurement circuit.
  • Figure 14 clearly shows that the comparison is no longer between the BER 10 ⁇ 6 (FR2) signature and the BER 10 ⁇ 3 (FR1) signature(as shown in Figure 13, they are generally too near to each other), but instead between the BER 10 ⁇ 6 (FR'2) signature and a reference FRR (IF) signature drawn at IF, i.e. where the selective fading parameters exceed the threshold that causes the alarm activation.
  • FR2 BER 10 ⁇ 6
  • FR1 BER 10 ⁇ 3
  • IF reference FRR
  • the FRR curve at IF is the curve corresponding to the selective fading distortions evolving towards an error condition for the adopted type of modulation-demodulation (in this case 4 QAM/34 Mbit).
  • Figure 15 shows a preferred embodiment of the device according to the invention.
  • the first part of the device that is the distortion detector, is substantially the same circuit as shown in Figure 12: it includes a transmission means symbolically represented by block H ( ⁇ ) (10), an AGC (B0) with amplifier AM (11), selective filter Fs (12) and detector (13), and the two branches, each one of which includes block B1 or B2, respectively, with curves having equal slopes, but opposite signs, and detector R1 or R2, respectively.
  • Signals A and B at the output from R2 and R1, respectively, are subtracted in S1 and summed up in A1.
  • Signal S2 at the output from S1 is applied to the two blocks B3 and B4, the voltage frequency characteristics of which are represented inside the rectangle of the related block; said characteristics (V vs f) are equal but symmetrical with respect to the central frequency (fc) of the data spectrum.
  • a reference voltage VRef is applied to adder A1 of A and B, and an output signal S3 is applied to block B5 that has the characteristic V (f) centered in f C .
  • Enabling AB for block B5 is given by circuit 15 that receives outputs 18 and 19 from blocks B6 fed by A, and B7 fed by B, respectively.
  • Signals 20 at the output from B3, 21 at the output from B4 and 22 at the output from B5 are applied to another circuit 25 (nNAND, nNOR or similar, as in 15) that supplies an alarm signal ALL.
  • the distortion measurement also allows to embody an adaptive equalizer using dissymmetry detection of the data spectrum; more particularly, the invention refers to a system for obtaining an efficient countermeasure to selective fading by means of adaptive equalization of amplitude only at intermediate frequency (IF), i.e. equalizing any distortion of the transmission channel module and leaving the group delay distortions unaltered.
  • IF intermediate frequency
  • adaptive equalization is made with the distortion measurement, i.e. the amplitude dispersion carried out by the power measurement of the data spectrum around 'n' frequencies.
  • dispersion detection over the whole band is made by using dissymmetry measurement, and this measurement drives an equalization structure in a critical manner.
  • the related device includes a delay line and a multiplier in the equalizer and a rotation block of the equalizer signal, two adder notches, two detectors and one comparator in the dissymmetry tester.
  • Figure 16 shows an equalizer made up of a delay line T1 installed in parallel to multiplier CM having a multiplying coefficient A1, while the measurement system for the data spectrum dissymmetries works on the signal u(t) at the output from the equalizer.
  • the input signal e(t) to be equalized is applied to T1 and CM, the output signals 1 and 2, respectively, of which are summed up in adder S1, from where the equalized signal u(t) is outputted, on which, according to an important feature of the invention, the measurement system of dissymmetries works after the equalizer.
  • Said signal u(t), as regards dissymmetry detection, is summed up in two different adding notches NS1 and NS2; in the first notch NS1, the signal u(t-T'1) coming from delay line T'1 (connection 3) and the signal u(t) (connection 6) are summed up.
  • the second adder NS2 sums up the signal u(t-T'1) (connection 5) and signal - u(t) drawn from the 180° end of rotation block B1 (line 7).
  • the signals 9 and 8, respectively, outputted from NS1 and NS2, respectively, are each applied to the detector R1 or R2, respectively and, the two measured voltages V1 and V2 are compared in notch D that calculates the difference.
  • the comparison signal D12 is sent back to the multiplier CM, that supplies the equalizing factor to S1.
  • Figure 17 shows a circuit which is substantially equal, except that the equalizer is made up of a feedback structure shown on branch 4 and comprising delay line T1 in feedback and multiplier CM with multiplying coefficient A1.
  • the measurement system for the dissymmetries driving said equalizer is made in a similar way as that shown in Figure 16, including the phase shift block B1, the two summing notches NS1 and NS2, the two detectors R1 and R2 and the comparator D.

Claims (13)

  1. Verfahren zum Erfassen von Verzerrungen des Datenspektrums in übertragenen digitalen Signalen (e'(t)), insbesondere Verzerrungen aufgrund von Interferenzschwund, um ein Schaltkriterium zu erzeugen und um das Spektrum adaptiv zu entzerren, dadurch gekennzeichnet, daß
    das erhaltene Signal (e'(t)) zwei parallelen Verzerrungen (B1, B2) unterworfen wird, die bei Frequenzänderungen Steigungen gleicher Größe, aber entgegengesetzten Vorzeichens aufweisen, wobei jede der Verzerrungen im Übergangszustand eine Änderung in der mittleren Leistung des Spektrums verursacht; daß
    die beiden mittleren Leistungen gemessen werden, die sich aus den beiden parallelen Verzerrungen ergeben; und daß
    die sich aus diesen beiden Messungen ergebenden Signale verglichen werden;
    wobei die Gleichheit oder die Ungleichheit der gemessenen mittleren Leistungen das Nichtvorhandensein bzw. Vorhandensein von Schwund anzeigen.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß, wenn Schwund vorliegt und die Notch-Frequenz (fo) des Schwundes von der Mittenfrequenz (fc) des Datenspektrums verschieden ist, die die Leistungspegel betreffenden Spannungen verglichen werden, wobei die Differenz zwischen den beiden Spannungen das Vorhandensein von Interferenzschwund anzeigt und ob die Notch-Frequenz (fo) auf der linken oder rechten Seite der Mittenfrequenz (fc) liegt.
  3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß, wenn Schwund vorliegt und auch wenn der Schwund eine Notch-Frequenz (fo) aufweist, die gleich der Mittenfrequenz (fc) des Datenspektrums ist, die gemessenen Spannungen verarbeitet werden, um eine Verzerrungsmessung zu erhalten.
  4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß ein Schaltkriterium oder Steuersignal erzeugt wird, um dem Interferenzschwund entgegenzuwirken, der Verzerrungen des Datenspektrums einer Übertragungsträgerwelle erzeugen kann, wobei die Messung der Verzerrung des Spektrums bei einer Zwischenfrequenz ZF ausgeführt wird, und wobei die Informationen aus dieser Messung verarbeitet werden, um bezüglich einer Bitfehlerrate (BER) von 10⁻⁶ eine ZF-Signatur zu erhalten, wobei die ZF-Signatur eine Kurve darstellt, die den Verzerrungen aufgrund des Interferenzschwundes entspricht.
  5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß bei der Zwischenfrequenz (IF) durch Einwirken auf nur die Amplitude ein Ausgleich der Verzerrungen erfolgt, wodurch jede Verzerrung auf dem Übertragungskanal ausgeglichen wird und die Gruppenlaufzeitverzerrungen unverändert bleiben.
  6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß die Dispersionserfassung bei der Zwischenfrequenz (IF) über das gesamte Band ohne die Verwendung von Filtern ausgeführt wird, wobei die entsprechenden Asymmetrien gemessen werden und das sich aus dieser Dispersionserfassung ergebende Signal den Entzerrer steuert.
  7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß die Messung der Asymmetrie am Entzerrersignal ausgeführt wird.
  8. Vorrichtung zum Ausführen des Verfahrens nach Anspruch 1, dadurch gekennzeichnet, daß die Vorrichtung
    zwei parallele Verzerrerblöcke (B1, B2) zum Verursachen von Änderungen in der mittleren Leistung des Spektrums im Übergangszustand, wobei die Verzerrungen bei Frequenzänderungen Steigungen gleicher Größe, aber entgegengesetzten Vorzeichens aufweisen;
    zwei Meßgeräte für die mittlere Leistung (R1, R2), von denen jedes einem der beiden Blöcke zugeordnet ist; und
    einen Komparator (A0; S1, D) für die Signale aus den Leistungsmeßgeräten enthält.
  9. Vorrichtung nach Anspruch 8, dadurch gekennzeichnet, daß jedes der Meßgeräte für die mittlere Leistung (R1, R2) eine Spannung abgibt, die gemäß einer bestimmten Kennlinie auf den Eingangsleistungspegel bezogen ist.
  10. Vorrichtung nach Anspruch 8 zum Ausführen des Verfahrens nach Anspruch 4, dadurch gekennzeichnet, daß, zusätzlich zur Schaltung für die Verzerrungsmessung, eine Schaltung vorgesehen ist, die aus wenigstens zwei Triggern (B3, B4, B5), besteht, von denen einer, vorzugsweise der Trigger, der die Meßsignale aufaddiert, auch mit der Bezugsspannung versorgt wird, die das Nichtvorhandensein von Schwund anzeigt.
  11. Vorrichtung zum Ausführen des Verfahrens nach Anspruch 5 und 6, dadurch gekennzeichnet, daß die Vorrichtung eine Verzögerungsleitung (T1) im Entzerrer, einen Multiplikator (CM) und einen Addierer (S1) enthält, und daß die Einrichtung zur Messung der Asymmetrie einen Rotationsblock (B1) für das Entzerrersignal, zwei Notch-Addierer (NS1, NS2), zwei Detektoren (R1, R2), einen Komparator (D) und eine Leitung (D12) für das Zuführen des Komparatorsignals zum Multiplikator umfaßt.
  12. Vorrichtung nach Anspruch 11, dadurch gekennzeichnet, daß der Multiplikator und die Verzögerungsleitung des Entzerrers parallel angeordnet sind, und daß ein Zweig der Einrichtung zur Messung der Asymmetrie eine zweite Verzögerungsleitung (T'1) enthält.
  13. Vorrichtung nach Anspruch 11, dadurch gekennzeichnet, daß der Entzerrer bezüglich des Multiplikators (CM) eine Rückkoppelstruktur aufweist, und daß die Verzögerungsleitung im Rückkoppelzweig in Reihe zum Multiplikator angeordnet ist.
EP90119037A 1989-10-27 1990-10-04 Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren Expired - Lifetime EP0427951B1 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
IT02216089A IT1237649B (it) 1989-10-27 1989-10-27 Sistema e dispositivi per l'equalizzazione adattativa dello spettro dati
IT02215989A IT1237648B (it) 1989-10-27 1989-10-27 Sistema e circuito di rivelazione delle dissimmetrie dello spettro dati in trasmissione in particolare di quelle dovute a fading seletti-vo
IT2216089 1989-10-27
IT2215989 1989-10-27
IT02223189A IT1237669B (it) 1989-10-31 1989-10-31 Sistema e circuito per la generazione di un criterio di scambio come contromisura ai fading selettivi.
IT2223189 1989-10-31

Publications (3)

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EP0427951A2 EP0427951A2 (de) 1991-05-22
EP0427951A3 EP0427951A3 (en) 1992-09-02
EP0427951B1 true EP0427951B1 (de) 1996-01-03

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EP90119037A Expired - Lifetime EP0427951B1 (de) 1989-10-27 1990-10-04 Einrichtung zur Erzeugung von Schaltkriterien und zur adaptiven Entzerrung von Datensprektren

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US (1) US5285473A (de)
EP (1) EP0427951B1 (de)
JP (1) JP3216094B2 (de)
DE (1) DE69024613T2 (de)
ES (1) ES2081332T3 (de)

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US6954702B2 (en) * 2003-02-21 2005-10-11 Ric Investments, Inc. Gas monitoring system and sidestream gas measurement system adapted to communicate with a mainstream gas measurement system
US7242725B2 (en) * 2003-04-02 2007-07-10 Harris Stratex Networks Operating Corporation Adaptive broadband post-distortion receiver for digital radio communication system
US20080084345A1 (en) * 2006-07-19 2008-04-10 Sensis Corporation Broadband multi-channel detector with signal and jamming discrimination
US8634766B2 (en) * 2010-02-16 2014-01-21 Andrew Llc Gain measurement and monitoring for wireless communication systems

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US4054842A (en) * 1977-01-19 1977-10-18 Rockwell International Corporation Channel gain imbalance compensation for FSK demodulator
US4200840A (en) * 1978-10-06 1980-04-29 The United States Of America As Represented By The Secretary Of The Air Force Dual detection scheme for compressive receivers
JPS5827475A (ja) * 1981-08-11 1983-02-18 Hitachi Ltd ゴ−スト除去装置
WO1985005518A1 (en) * 1984-05-15 1985-12-05 Australian Telecommunications Commission Characterisation of digital radio signals
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EP0427951A3 (en) 1992-09-02
JP3216094B2 (ja) 2001-10-09
EP0427951A2 (de) 1991-05-22
DE69024613D1 (de) 1996-02-15
JPH03187611A (ja) 1991-08-15
DE69024613T2 (de) 1996-08-01
ES2081332T3 (es) 1996-03-01
US5285473A (en) 1994-02-08

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